Ok so vs anyone early game u shouldnt play to agressive, try to grab people and do the most damage possible succesfully do it, farm as well as u can but dont lose too much health. Also try to Grab the cannon minion if u cant get it with basic atacks and use spells to kill minions but be careful with ur mana.
If ur behind or even ur ahead but near turret try to grab the enemie to it.And if ur too close to the enemie flash Q.

Since till u get some items blitz isnt that much of a pusher or wave clearer when u push ur lane ROAM, ur the best champ to do it and u have very low CD on ur ulti so when ur back to lane u have it again.Dont worry to use Flash or Ignite for a kill, if ur sure u can get it or u have a big chance of geting it.

In late game where the fights start tell ur team that they should wait for u to grab someone if u havent a good engage on ur team.
But if u do have a good engage like (Vi,Hecarim,WW etc.) let them engage and flash into the middle of ur enemies and use ur ULT, it will silence them and ur team can get a huge advantage out of that.
Also when ur enemies are Drake or Baron and ur on the other side of the wall or in a good position try to catch their jungle(mainly if u can do it) or any of their members this way u will have number advantage and get that bonus money or baron buff with could turn the game.
Also try to ward agressivly and defensivly so u can sneak on ur enemies and surely instakill them if its an squichy one. But if it isnt just call ur team.